The term “Prosthetic Liner” is used to describe any of many various “sock-like” medical devices worn by amputees to protect their residual limb. Although the majority of the following disclosure describes the prosthetic liner in terms of a leg amputation, the present invention is not intended to be limited to leg amputations and also finds practical applications to other prostheses such as for an arm amputation. The liner is often worn directly over the residual limb of the amputee, and consists of a soft interfacing material (Gel, Silicone, Polyurethane) affixed to a more durable outer layer (often fabric constructed of Nylon or Polyester). The traditional process generally involves either one or two pieces of shaped fabric that are sewn together on all sides except the top to form a proximal open-end tubular-shaped fabric member or tubular “sock”. The tubular-shaped fabric is then often placed into an injection molding machine and coated with hot gel or silicone that adheres to the inside surface of the tubular fabric to form the soft inner layer. The purpose of the liner is to provide both comfort to the residual limb of the amputee, and to allow the residual limb to slide into (and fit comfortably once inside) a molded prosthetic socket. Such liners commonly come in two styles: cushion liners for suction suspensions, and liners with threaded distal encapsulations for lock and pin suspension systems. A brief search of the Prosthetics Industry will show that these styles of prosthetic liners have been the preferred style of liner over the last several decades.
When the amputee uses a prosthetic device, the amputee simply attaches a prosthetic limb to their residual limb by means of a rigid socket, liner, and a suspension means. The rigid socket can be custom fabricated to match the shape of the intended user's residual limb and can be formed from a variety of different materials, including but not limited to thermoplastic materials, fiber-reinforced thermoset materials, as well as woods and metals. Because the residual limb interfaces with the hard, rigid prosthetic limb, this interface can become an area of discomfort over time since this interface is a load bearing interface between the residual limb and the prosthetic limb. In order to alleviate this discomfort and provide a degree of cushioning to lessen the impact of the load, prosthetic liners are used as interface members between the hard prosthetic socket and the residual limb in order to increase comfort.
The more recent preferred style of liner such as that disclosed in U.S. Patent Application Publication 2011/0270414 A1, incorporated herein by reference, consists of an inner layer of gel, silicone, or polyurethane material that adheres to an outer layer of fabric. One method of manufacturing this traditional liner involves taking two separate pieces of identical die cut fabric and sewing them together on all sides, excluding the top, to form an integral open proximal ended tubular piece of fabric. This open proximal ended fabric “sock” is then placed in a molding apparatus and injection molded with a hot gel polymer, which bonds to the inside of the outer fabric, to form one version of the modern standard of liners noted above. This version of the standard liner has stitching running all the way around the liner that divides the liner into two distinct sides, i.e., an anterior side and a posterior side with the stitching extending along the sides of the residual limb when worn.
Although the present invention is illustrated and disclosed herein as having two distinctive sides, i. e., anterior and posterior sides, it is not intended to be limited as such. For example, the two distinctive sides of the liner could be disposed on the left and right sides of the residual limb when worn with the stitching residing along the anterior and posterior sides of the limb. Also, the present invention may have more than two distinctive fabric layers such as three or four or even five pieces of die cut fabric sewn together on all sides, excluding the top, to form an integral open proximal ended tubular piece of fabric. Furthermore, the pieces of fabric do not have to be identical and could be customized according to an amputee's needs.
Most of the available cushioned residuum prosthetic liners that are currently available have a tubular or conical construction. While intended to provide the best fit to the residual limb, at times they cannot provide the best form fit of the amputee's residuum since the residuum stump typically does not contain a completely uniform shape. For example, while a residuum stump generally may have a conical shape, the residuum stump will often have recessed areas in certain locations. A stump may generally have a conical or cubical shape with invariably recessed areas on, e.g., the medial side of the prominent tibia bone. Generally, for a BTK amputee, the left side residual limb will have the recessed area predominantly on the right side of the tibia bone. There is also typically a smaller recessed area on the left side. On the right side residual limb, the predominant recessed area is on the left side of the tibia bone, with smaller recessed areas on the right side. Usually the greatest recess occurs immediately below the patella, on either side. In addition, left side amputees typically have a right side bias to the bony prominence of the below knee stump, and right side amputees have a similar bias to the left side. Unfortunately, there are also recesses formed in the residual limb caused by injury. Conventional tubular or conical elastic liners simply cannot account for these several variable conditions without using extremely high levels of elastic tension which compress the outer-most points along the stump's circumference, causing discomfort and a non-uniform fit. Conventional prosthetic liners do not accommodate the non-uniform nature of the residuum and this can result in the amputee experiencing wearing discomfort due to the non-uniform fit.
Furthermore, many amputees experience a swelling of the stump. When the residuum is in a prosthetic socket the stump tends to contract significantly, and when taken out of the socket the stump tends to expand within minutes of removal. This expansion and contraction of the residuum contributes to the development of air pockets and the generation of obtrusive noises since a liner which may have provided a comfortable fit on the expanded stump becomes a loose fit with air pocket opportunities when the residuum is placed inside the prosthetic socket. In addition, and over time, an amputee's residuum tends to adjust in size, usually shrinking. As these changes occur they increase the tendency for the pistoning effect, described above, to occur. In addition to the embarrassment caused by the sound effects generated by pistoning, cushioned socks which allow or promote air pocket formation quickly wear out and, if not replaced often, lead to lesions, etc. on the residuum.
Maximum comfort is critical component to the amputee (and consequentially, to their prosthetist) during their search for the correct prosthetic liner. As such, many different manufacturing features can be added or altered in order to enhance the basic liner concept highlighted above. For instance, as disclosed in U.S. Patent Application Publication 2011/0270414 A1, the stretch and thickness characteristics of the external fabric are often altered to allow greater ranges of motion for varying parts of the residual limb. As disclosed in U.S. Patent Application Publication 2005/0101693 A1, incorporated herein by reference, the thicknesses of the internal layer can be altered by tapering or adding extra padding to sensitive skin areas, while reducing bulk and un-necessary material and weight in other areas. It is well established in the marketplace that gel strips or foam padding are often attempted to be added to the outside of the prosthetic liner (between the liner and the socket) to make up for volume fluctuations in the residual limb of the amputee that occur throughout the course of the day, or to make up for an ill-fitting permanent prosthesis. Items designed to serve these functions have been available for years, but the inherent difficulty lies in affixing them to the outside of the traditional liner and having them remain in this intended position inside the socket over the duration of the normal usage period. As disclosed in U.S. Pat. Nos. 6,149,691 and 6,923,834, foam or pneumatic padding is often added to the socket to improve the fit in the case of amputees not being fitted correctly into their socket. As disclosed in U.S. Pat. No. 1,319,637, the prosthetic liner includes a series of woven or knitted stump socks secured to each other at their distal ends. Each layer is adapted to be rolled upon the residual limb to provide pockets for receiving padding between the layers.
Although the above discussed prior art devices are intended to enhance comfort for the user, they do have drawbacks. Either the padding is molded into the existing material during manufacture, or adhered to existing surfaces of the liner or socket or both, or permanently disposed between layers of the liners. Although the last prior art device mentioned does have an elastic pad disposed between the fabric layers, the pad must be held to the inner layer before the outer layer is rolled up and over the pad to hold it in place which is a complex operation with no guarantees that the pad will remain in the desired position.
Thus, there is still a need in the art for a prosthetic liner which overcomes the deficiencies of the prior art and is constructed so that padding could be easily inserted into or removed from the liner with minimal effort on the part of the wearer. This need is not only limited to comfort padding, but extends to other therapeutic applications such as heat therapy as is discussed hereinafter. The “pocket(s)” created by the additional layer(s) of fabric in the present invention provide enormous potential to the end user.